Revisiting energy transfer in Tm-doped aluminosilicate glass fiber III: quantifying the blue emission

This study characterizes, for one value of the Tm 3+ concentration, the populating and de-populating mechanisms of the 1 G 4 level of the Tm 3+ ion in an aluminosilicate glass host under standard 790 nm pumping conditions. The 3 H 4 , 3 H 4 → 1 G 4 , 3 F 4 energy transfer upconversion (ETU) microscopic rate parameter is determined to be 5 +/-0.5 s -1 , which was obtained using the fluorescence rise time after pulsed excitation of the 3 H 4 level. We also provide evidence that the 1 G 4 level is initially populated by pump excited state absorption at lower pump power, however this process makes a minor relative contribution to populating the 1 G 4 level compared to ETU, in the limit of high power and for the Tm 3+ concentration considered in this study. Quantification of the de-populating energy transfer processes of the 1 G 4 level was achieved after direct excitation at 465 nm, resulting in the total microscopic rate parameters for all cross relaxation and ETU processes relevant to this level being 4,000 +/- 250 s -1 and 2,500 +/- 500 s -1 , respectively. The energy migration rate of this level was determined to be 1550 +/- 150 s -1 . This report also provides a more general form of the intrinsic decay time calculation for each energy level of Tm 3+ -doped aluminosilicate glass as a function of Al 2 O 3 content, which is based upon the modification of the non-radiative decay rate of Tm 3+ -doped silica from adding Al 2 O 3 .